Electromagnetic device



April 2, 1935.

M. .1605 ET AL ELECTRMAGNET IC DEVICE Filed Jan. 15, 1953 2 sheets-sneak 1 WVFA/TO/PS' M Jaas 5. v. BABE/77' April 2, 1935. M. .1008 ETAL ELECTRMAGNETI C DEVI CE Filed Jan.'13, 1953 V 2 Sheet s-Shee t 2 /mum? Patented Apr. 2, 1935 v r v r I l UNITED TES =35? Martin Joos, Alma Center, Wis., land Bethel J.

Babbitt,Riverside,v1ll., assignors to Wcstern Electric Company, Incorporated, New .York, N. Y., a corporation of, New York Application January 13, 1933, serial No. 651,488 19 Claims (01. 175-483) This invention relates to an electromagnetic de- .ing [4 for pp y a mas v ft th viceand more particularly to an electrical meas-' specimen; In order to provide a good magnetic ui'in'g device; I contact between the pole pieces and the specimen;

In measuring the magnetic properties'of highly a clamp [5 is provided in the aperture H of each 5 permeable magnetic materials, the difficulties of pole piece and'this clamp is urgedupwardly by 5 obtaining accurate 'resultsincrease ,with higher a pair of helicalsprings l6. Inorder to separate perm'eabilities. V the clamp to permit the insertion of the specimen,

An'object of the present invention is to provide the yoke is provided with a pair of vertical aper an accurate and efficient electromagnetic device; tures through which astaple l7 extends to cqn 10 In accordance with one embodiment of the intact with the top face of the clamp to'urge-the 10 vention, a permeameter or' induction meter is proclamp downwardly until the end of the specimen vided-having a rotatable detector responsive to is inserted between the clampand-the pole piece. the leakage flux from two points on the specimen The yoke is provided with a compensating Windbeing measured,v in' which the detector and the ing l8, which is preferably made in anumber of 15. portion of the specimen being measured are ensections, one section being applied to eac'l ijeg Of closed in a magnetic shield having means for the yoke; V H v a, eliminating remanence and reducing" hysteresis Superimposed upon'the magnetizing winding 1 losses. The permeameter ispr oyided with a yoke it and co-axial therewith is an induction wind: of a nickel-iron alloy havingldistributeidair gaps ing E9; which is preferably located centrally or whereby high initial permeability and low coercive qthe magnetizing winding, and a pair of. pole gg force are attained and the'yoke is provided with pieces 2| [extends to points of the'magnetizing a winding for equalizingthe time constants of winding adjacent the ends of; the induction windthe windings on the yoke and the magnetizing ing. The inner ends ofthesepolepieces are er-'- and induction windings in order to obtain a true cuate andanarmature 22 is adapted to rotate 25 reading of induction. l 1 f therebetween. The armatureconsists'of acore 2 A complete understanding of theiinvention may of magnetic Qmaterial having a high. initial perbe had by reference to the following description meability, such as' a nickel-iron alloy, and'the taken in conjunction .with. the accompanying core isprovided with anarmaturewindifig The armature is supported on the shaft 123 which may drawings, in which Fig. l is aperspective view. partlyjin section be rotated by means of a motor 24 1n-orq r 30 illustrating an embodimentofjthe invention; and to eliminate the effect of stray flux, the'armature,

Fig. .2 is a circuit diagram of the apparatus as well as the induction coil and that portion'of illustrated in Fig. 1. I j p the magnetizing windingcontainingthe portion The apparatus may ,be mounted on a base 6' of the specimen to be measured, is enclosed in a,

provided with a'cover creasing I hinged to the agnetic shield 25. shield is preferablya5 v basealcng the back side. Mounted upon'the base ad of two-parts, as shown in the drawings; is a U-shaped y k 8 c n i n of a p u a the lower part being secured to the base 6 and laminations of a magnetic material havinga high th pper part being attached to the icfasingl by i ial p rm a i and Wc e v v h means of bolts 25 so that in raising the casing 40 as a nickel-iron alloy. 1 The yoke is U-shaped in r the Shield will Separated a ov 40 .f and 994311 leg of the yoke iol'ms in effect toflthe armature 22. The. shield is of a 7 section'- Thse Sections are preferably mail magnetic material having ahigh initial prmea vvidually mounted on'the baseand arranged in abutting relation so as to provide aminute air gap between the sections. The low coercive force,

together with the distributed air gapsin the yoke, I v I produces a low remanence orre'sidual magnetism accomphshed b pro'vldmg the Shield 1 in the yoke 'rality of'apertures 21 extending over the;

The open ends of the k i d w t shield. Theconductorsof an alternating current bility, such asa, nickel-iron alloy fand order to preventv magnetization from the shielditself,

pole piecesfQ ghaving apertures .llftherein and Winding e a three Phase n am 50 andsurr'oundingtheisleeveisa magnetizingiwind detector unit are also preierably I a sleeve 12 of non-magnetic material, such as r p r I brass or cardboard, extends from annaperture, in a by pa ng ll e na e u nt one pole piecetothe other. The sleeve isadap'ted ns a cont nu us id agsn ti ns .fq ijis to receive therein a specimen L3 to be measured applied to the shield. The p lehp eces i go! the shield is continuously dema netized; 4 V

threaded backand forth through the apertures r equipped with a demagnetizing winding threaded through apertures in the pole pieces.

. 'When there is a difference in magnetic potential at the ends of pole pieces 2| which are adia-' cent the specimen being measured, a current will be generated in the detector coil ofiarmature 22 .which is led through slip rings 28' to an input circuit 29 of a thermionic tube amplifier, theoutput circuit 31 of which is connected to asecond pair of slip rings 32 also on shaft 23. This shaft also carries a two-part commutator 33 and. one of; the slip rings 32 is connected to one part of the' V commutator and the other slip ring 32 to the other part of the commutator. The 'cornmutatorrectifies the current delivered from the amplitl er and directs it to a galvanometer 34.

In measuring the permeability, ofspecimen,

the specimen to be "measured is placed within the magnetizing. winding and clamped between the pole pieces. In order to apply ainagnetomoti-ve force" to the specimen, a source 'of'di'rect cur renten'ergy 35 is provided havingahammeter 36 its upper contacts. .The' first step ,in'measuring 1thej1'inductance consists in dema'gnetizing the 1o] [flow through the. magnetizing. winding. and

and a variable resistance 3| in circuit therewith. The source of energy may be'c'onnected to the magnetizing winding byclosing a'gang switch 38, a reversing switch 39 and closing a switch 4| on specimen-f: This is accomplished byadjusting the resistance 37 so as to cause a ratherhigh current intermittently reversing switch 39,. "The-current I is me eauced'by adjusting resistance "31 and the current is again reversed anumber of times.

This process is continued'until the current is reduced, to zero; The motor, 24 is then started'and resistance 31 is'then set'so asto allow a current to flow-which will provide a magnetomotive force ;at which .the specimen is to be testedr A switch} 42 is 'thenjclosed which causes a'icurrent to be appliedto the compensating winding I 8 irom' 1 a w direct current source 43"having an ,ammeter-M infcircuit therewiththr'oughon'e of the variable resistances 45 and 46, depending upon whichflcon-j tacts theigang switch is closed upon; The-resistance 45or 45 1s then varieduntilithe 'galvanometer 34-reads zero, atwhich time the magnetic poten tial dropdri'the portion of the. specimen being 7 tested will be equal to the magnetomotive force applied. tofthis-portion of the specimen, and at thistim'e .therewillbe no difference of potential V at the points on the magnetizing winding atwhich thepcle 'piecesiZl engage therewith and, therefore,"noleakagefiux'injjthe armature field.v The f gang ,switch38fisthen reversed, which reverses both the magnetizing current and the compen "s'atin'g current. The compensating; current is fthenfagainl adjusted by. means of theresistance 45hr 46' until the galvanometer 34 reads zero.

It has been-round that the resistances "45 and 46 when the'adjustment issuch that a reversal of the gang-switch causes no'deilection in the galarenot; necessarily'equaland in fact usually vary -v'anonieter 34. This'is 'duefto the residual induction in the yoke which islargely overcomeby'r'epeated -rei ler'sals ofthe gangswitchl After the apparatus isadjusted so that the magnetic potential dropin the portion'of the specimen being measured .is equal to the magnetomotiveforce applied thereto the gang; switch is reversed and V theenergy in the inductionof the specimen is ap {plied to the'induction winding l9, the magnitude .of which isfindicatedaby agalvanometer 411m 4 circuit therewith,

' It iisivide'rit thatif the time constants of the tion.

induction winding. and the Winding on the yoke are not equal, the galvanometer 41 will not always indicate the true induction in thespecimen. This dihiculty is overcome by providing anequal izing winding 48 on theyoke which has a varia sistance may be 'varieduntil' the time constants of theinduction winding and theyoke windings are'equal. r 7

In plotting an induction curve of a specimen, it may be necessary to have available a larger scale than is provided by galvanometer .41. For

this purpose a switch-5| is provided which, when closedon its uppercontacts, provides a direct,

"connection betweenthe circuit-of the induction coil andthe galvanometer and whenthis switch is on its lower contacts, a known or predeter:

mined resistance is placed in the galvanometer i v circuit to place the galvanometer, on a different -scale.,. .1 v i It may at times become'necessary to'check the the operation of galvanometer 41. Forthispurpose a. mutual inductance 52 is permanently placed in the galvanometer circuit so that its eifect will be the same during calibrationlas in paratus. The switch 4| when closedon its lower contacts connects the mutual inductance to the source of energy 35 'andbyireversing the'switch' 39 a transient currentsimilar to'thatused in measuring is applied to .the ga'lvanometer. It will be understood that the nature and em bodiment of the'inventionfherein 'described is merely illustrative and that many changes and 'modificationsm'ay be made therein withOutdeble resistance '49 in circuit therewith.- This re parting from the spirit and scope of the inven- V fwhat isf claimed sr 1 1. A measuring ,japparatus specimen, means for determining the equality of said quantities including an armaturefrotatable in the leakage flux of the specimen'and havinga core of highinitial permeability, and means for measuring the magnetic induction in the speci men. v 2. A ,mea'suring apparatus f comprising means for impressing a magnetomotive force on aspecimen 'equalito the magnetic potential drop in the I comprising means ior impressing a'magnetcmotiv'e force on a'speci men equal tothe magnetic potential drop in the.

specimenfmeans for .determiningjthe equalityf of said quantities including an armature rotata ble in theleakage flux'of the 'specimenand'having a coreoi anickel-ironialloy of high initialpermeability, and means for measuring 'the mag} netic induction in the specimen- 8. A measuring apparatuscomprising means 7 for. impressing a magnetomotive forceona speci-,

men equal to the magnetic 'potential'drop' injthe specimen, a. rotatable armature havingf a; core of magnetic material, 'a pair of, polelpieces 'adJa cent the armature andexten'ding'toflpoin'ts adja cent the.,ends otgthe portionof the, specimen .being i measured, indicating" meansgassociated with the armature to indicate "the "amount '0':

leakage .flux from saidpoints of the. specimen,

'andmean's for indicatingth'e magnetic lnduction in the specimen,

Q 4. A measuring apparatus" comprising'tayoke of magnetic material having distributed air gaps,

a compensating winding on the yokega'winding extending across the endsot the yoke .iorreceivfmeasuring the induction in the specimen; .1

" 5; A measuring apparatus comprising a yoke ing a specimen to be 'measuredia'nd meansior of a nickel-iron alloy having a high initialpermeability and provided with distributed air gaps, a compensating winding on theyoke, a winding extending across the ends of the yokefor receiving a specimen to be measured, and means for measuring the induction in the specimen.

6. A measuring apparatus comprising a yoke of magnetic material having an air gap, a compensating winding on the yoke,-a winding exendingacross the endsof the yo ke, for receiying a specimen to be measured, and means 7, for.

. measuring the induction in the specimen.

7. A measuring instrument comprising a magnetizing: coil for receiving a specimen to be measured, an induction coil co-axial therewith, a magnetic shield enclosing the portion of the specimen tobe measured, andmeans fordemagnetizing the-shield. I I

8. In an electromagnetic device, means affected by magnetic lines of force, ashield for said means, and means for Idemagnetizing the shield] 9. In an electromagnetic device, means'afiected by magnetic lines of force, a shield for said means, and means for applying an alternating magnetic flux to the shield to maintain the shield demagnetizecl. I

10. In an electromagnetic device, means affected by magnetic lines of force, a shield for said means, said shield having a plurality of apertures, and insulated conductors passing through said apertures for receiving a demagnetizing current.

11. A measuring instrument comprising a magnetizing coil for receiving a, specimen to be measured, a pole piece in close proximity to a point on said winding, and an armature'rotatable in the magnetic flux from said pole piece to measure the magnetic leakage from said'point. v

12. A measuring instrument comprising a magnetizing coil for receiving a specimen to be meas- I ured, a pole piece in close'proximity to apoint on said'winding, an armature rotatable in the magnetic flux from said pole piece to measure the magnetic-leakage from said point, and means for applying a demagnetizing force to the pole piece. I i

, 13. A measuring instrument comprising a magnetizing coil for receiving a specimen to be measured, an armature, and pole pieces adjacent the armature and extending to spaced points on the winding.

14. A measuring instrument comprising a mag- 'netizing coil for receiving a specimen to be meas ured, an armature, pole pieces adjacent the armature and extending to spaced points on the winding, and means associated with the pole pieces for preventing remanence and reducing hysteresis losses ther'ein.i V

15. A measuring instrument comprising-a yoke, a compensating winding thereon, a magnetizing:

winding for receiving a'specimento be measured, an induction winding'co-axial with the .magnet-.-

izing winding, a movable induction type detector for leakage flux from the specimen, an amplifier; associatedwith the detector, and an indicating deviceoperable by said amplifier. I

'16. A measuring instrument comprising a magnetizing winding for receiving a specimen to be I measured, a yoke subtending the ends, of said winding, a compensatingwinding on the yoke to compensate for the magnetic potential drop in the specimen produced by the magnetizing winding, an induction winding co-axial with the magnetizing winding, and a winding on the yoke having a variable resistance incircuit therewith for equalizing the time constant of the windingson;

the yoke with the time constant of the magnetizing and induction windings.

17. A measuring instrument comprising amagnetizing winding for'receiving a specimen tobe;

measured, a yoke subtending the ends-of said winding, a compensating winding, on the yokeQa'.

source of energy for the "compensating windingfl a switch for reversing the direction of current in, Y i

the compensatingwindin and a pair of resistances, one of which is in thelcompensating winding circuit for one direction of current flow-"and the other of which isfin the compensating windingcircuit for the other direction of current flow'.

I 18. A measuring instrumentcomprising rneans said armature, and an indicator operable inresponse to saidrectified current.-

19. A measuring instrument comprising means for impressing a magnetomotive force on a specimen equal to the magnetic potential drop in the specimen, an armature rotatable in the leakage flux of the specimen for determining the equality of said quantities, means for amplifying thecurrent generated in said armature, and an indicat- I ing'device responsive to saidamplified current.

- MARTIN JOOS.

I BE'IHEL J. BABBITT. 

